Systems and methods for beam failure recovery enhancement

Abstract

Systems and methods for beam failure recovery (BFR) are disclosed herein. A user equipment (UE) receives downlink (DL) reference signal(s) on corresponding beam(s) from a base station. The UE performs beam failure detection (BFD) on such beams used for user data to determine whether a beam failure has occurred, and candidate beam detection (CBD) on such beams not used for user data to identify candidate beams for recovering from the beam failure. The BFD and the CBD are based on both uplink (UL) channel performance considerations and DL channel performance considerations, as determined using the DL reference signal(s), such that a beam failure may be determined in the UL, the DL, or both, and a candidate beam may be identified for UL, DL, or both. The UE sends a beam failure recovery request BFRQ with this information to the base station, and the system changes beams accordingly.

The invention claimed is: 
     
       1. A method of a user equipment (UE), comprising:
 receiving, from a base station, a plurality of reference signals, the plurality of reference signals comprising one or more first downlink (DL) reference signals configured by the base station for beam failure detection (BFD) and one or more second DL reference signals configured by the base station for candidate beam detection (CBD); 
 performing the BFD and the CBD based on both a DL channel performance and an uplink (UL) channel performance corresponding to measurements of the plurality of reference signals; 
 determining, based on the BFD, that a beam failure has occurred; and 
 reporting, to the base station, a beam failure recovery request (BFRQ) identifying a candidate beam detected during the CBD for recovering from the beam failure, wherein the BFRQ uses a medium access control control element (MAC CE) to identify the candidate beam, wherein the MAC CE indicates that the candidate beam is to be used as both an UL candidate beam and a DL candidate beam on a serving cell, and wherein the MAC CE comprises a first bit that indicates whether the serving cell has experienced an UL beam failure and a second bit that indicates whether the serving cell has experienced a DL beam failure. 
 
     
     
       2. The method of  claim 1 , wherein:
 the BFD is performed based on a comparison of measured layer 1 reference signal received power (L1-RSRP) of the one or more first DL reference signals to an L1-RSRP threshold. 
 
     
     
       3. The method of  claim 2 , wherein:
 the BFD is further performed based on a comparison of hypothetical block error ratio (BLER) calculated respective to the one or more first DL reference signals to a hypothetical BLER threshold. 
 
     
     
       4. The method of  claim 1 , wherein:
 the BFD is performed based on a comparison of virtual power headroom (PHR) measured respective to the one or more first DL reference signals to a virtual PHR threshold. 
 
     
     
       5. The method of  claim 4 , wherein:
 the BFD is further performed based on a comparison of hypothetical block error ratio (BLER) calculated respective to the one or more first DL reference signals to a hypothetical BLER threshold. 
 
     
     
       6. The method of  claim 1 , wherein:
 performing the BFD comprises performing UL BFD and performing DL BFD; 
 the UL BFD is performed based on a first comparison; and 
 the DL BFD is performed based on a second comparison. 
 
     
     
       7. The method of  claim 6 , wherein:
 the first comparison comprises a comparison of measured layer 1 reference signal received power (L1-RSRP) of the one or more first DL reference signals to a first L1-RSRP threshold; and 
 the second comparison comprises a comparison of the measured L1-RSRP of the one or more first DL reference signals to a second RSRP threshold. 
 
     
     
       8. The method of  claim 6 , wherein:
 the first comparison comprises a comparison of measured layer 1 reference signal received power (L1-RSRP) of the one or more first DL reference signals to an L1-RSRP threshold; and 
 the second comparison comprises a comparison of hypothetical block error ratio (BLER) calculated respective to the one or more first DL reference signals to a hypothetical BLER threshold. 
 
     
     
       9. The method of  claim 6 , wherein:
 the first comparison comprises a comparison of virtual power headroom (PHR) measured respective to the one or more first DL reference signals to a virtual PHR threshold; and 
 the second comparison comprises a comparison of hypothetical block error ratio (BLER) calculated respective to the one or more first DL reference signals to a hypothetical BLER threshold. 
 
     
     
       10. The method of  claim 1 , wherein:
 the CBD is performed based on a comparison of measured layer 1 reference signal received power (L1-RSRP) of the one or more second DL reference signals to an L1-RSRP threshold. 
 
     
     
       11. The method of  claim 1 , wherein:
 performing the CBD comprises performing UL CBD and performing DL CBD; 
 the UL CBD is performed based on a first comparison; and 
 the DL CBD is performed based on a second comparison. 
 
     
     
       12. The method of  claim 11 , wherein:
 the first comparison comprises a comparison of measured layer 1 reference signal received power (L1-RSRP) of the one or more second DL reference signals to a first L1-RSRP threshold; and 
 the second comparison comprises a comparison of the measured L1-RSRP of the one or more second DL reference signals to a second RSRP threshold. 
 
     
     
       13. The method of  claim 11 , wherein:
 the first comparison comprises a comparison of virtual power headroom (PHR) measured respective to the one or more second DL reference signals to a virtual PHR threshold; and 
 the second comparison comprises a comparison of measured layer 1 reference signal received power (L1-RSRP) of the one or more second DL reference signals to an L1-RSRP threshold. 
 
     
     
       14. The method of  claim 1 , wherein:
 the MAC CE is sent on resources granted by the base station in response to a scheduling request that is configured to be sent by the UE in response to the BFD. 
 
     
     
       15. The method of  claim 1 , wherein:
 the beam failure comprises an UL beam failure; and 
 the MAC CE is sent on resources granted to the UE by the base station in response to a scheduling request that is configured to be sent by the UE in response to the UL beam failure. 
 
     
     
       16. The method of  claim 1 , wherein:
 the beam failure comprises a DL beam failure; and 
 the MAC CE is sent on resources granted to the UE by the base station in response to a scheduling request that is configured to be sent by the UE in response to the DL beam failure.